Electrical circuits of this kind are desirable for use with four-pole devices, where an input and output connection should not be connected to the ground directly, because otherwise a part of the four-pole device would be short-circuited. Such four-pole devices include for example bridge circuits comprising at least four electrical elements and which illustratively are used for temperature measurement, voltage measurement, torque rating, tension measurement, magnetic field measurement, or for measurement of another physical quantity.
The four-pole device may also be any other electronic element whose equivalent-circuit diagram is a bridge circuit. For example, a Hall-element is such an electronic element. A switching arrangement of the afore-mentioned kind is known from U.S. Pat. No. 4,142,405.
Typically, the output signal of the four-pole device includes a useful or information containing component which is dependent on an input signal and an interference component which is independent of the input signal. (Illustratively the input signal is produced by a source which is connected in single pole fashion to the four-pole device).
An object of the invention is to provide a switching arrangement of the aforementioned kind where the polarity of an information containing component of the output signal of the four-pole device, can be reversed without reversing the polarity of the interference component at the same time. This reversion of polarity can be used, for example, to separate the information containing component of the four-pole device output signal from the interference component, which is independent of the polarity of the input signal. Illustratively, the interference component, is produced internally in the four-pole device and is a thermoelectric voltage resulting from the contact of different metals or, in the case of an AC fed four-pole device, a direct current component, which is created by non-linearity of the four-pole device. An additional interference component may be produced in the process electronics located at the output of the four-pole device, for example an offset voltage.